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Finding the Fourth Proportional to 761.40, 1,139.58 and 687.96

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Solution

The fourth proportional to 761.40, 1,139.58 and 687.96 is: 1,029.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    761.40 : 1,139.58 = 687.96 : x
  2. Step 2: Convert to fraction form
    761.40/1,139.58 = 687.96/x
  3. Step 3: Cross multiply
    761.40x = 1,139.58 × 687.96
  4. Step 4: Simplify right side
    761.40x = 783,985.46
  5. Step 5: Solve for x
    x = 783,985.46/761.40
  6. Step 6: Final answer
    x = 1,029.66

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.